03/07/2022

Working Principle of Fuel Cell

 Fuel cell

The fuel cells are electrochemical devices that convert the chemical energy of gaseous fuel directly into electricity.

  • The fuel cell principle was discovered by William R Grove, a British Physicist in 1839. 
  • A fuel cell consists of an electrolyte ( either solid or liquid ) sandwiched between two electrodes. 
  • The hydrogen gas passes over anode electrode with the help of a catalyst separate into electrons and hydrogen protons.

2H2 → 4H++ 4e-

  • The protons flow to other electrode called cathode through electrolyte whereas the electrons flow through an external circuit therefore creating electricity. 
  • The hydrogen protons and electrons combine with oxygen flow through cathode and produce water as only waste due to chemical reaction.

O2 + 4H+ + 4e- → 2H2O

Overall chemical reaction

2H2 + O2 → 2H2O



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Fuel cell efficiency

  • The fuel cell efficiency is greatly affected by quality of electrolyte. 
  • It increases with increasing the membrane ability to block electrons generated form the oxidation of the anode from reaching the cathode.
  • The electrolyte must be chosen carefully such that allows only position ions to pass through is in one direction only towards cathode. 
  • A catalyst is added in order to reduce the reaction energy on the two electrodes.




Parts of fuel cells

Membrane electrodes assemble ( MEA )

  • It is a compact unit producing output power of the fuel cells. Its thickness is in terms of few hundred microns. 
  • It consists of two electrodes with their catalyst and electrolyte.

Electrolyte

  • The electrolytes are thin plastic like / solid polymer / liquid membranes.
  •  Their main function is to pass the hydrogen positive ions from the anode to cathode while completely block the free electrons from moving in this direction. 
  • If the free electrons could pass through electrolyte, chemical reaction will be hold up.

Electrodes

  • Every fuel cell consists of two electrodes that are anode and cathode. A catalyst is required for each electrode.

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Types of Resolver

 

Catalyst

  • It is special chemical material used to increase the rate of reactions without being consumed. 
  • Most types of fuel cells used platinum ( Pt ) and its group as catalyst at the two electrodes. 
  • The Pt catalyst at the anode helps in splitting the hydrogen molecules into free electrons and positive protons. 
  • At the cathode, it enables oxygen reduction. 
  • A catalyst of a fuel cell is one which has high electric conductivity, stable contact the electrolyte and reactance gases.

Fuel cell voltage

  • The voltage produced from one cell lies between 0 to 1 voltage and depending upon operating condition, type of electrolyte and size of load connected to the fuel cell. 
  • The typical value of fuel cell is about 0.7 V. 
  • In order to higher voltage, multiple cells are connected in series. The total stack voltage

            = Average cell voltage × Number of cells

  • There is electrical resistance in the fuel cell, resulting heat loss occurs in it. The heat is released from the fuel cell reaction.

 

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